1. Field of Invention
The invention relates to a refractory ceramic plate and an accompanying wall structure for an incinerator, for example a garbage incinerator.
2. Background of the Invention and Description of Related Art
DE 44 20 294 C2 describes a basic wall structure for such a garbage incinerator.
According to this publication, the wall structure comprises a (mostly metallic) furnace wall, in which numerous pipes spaced apart from each other are arranged, through which a fluid, mostly water, flows during operation.
Anchors are secured to the furnace wall, which are essentially spaced perpendicularly apart from the furnace wall, and provide reinforcement in a ceramic compound lying adjacent to the furnace wall, downstream from which are the refractory ceramic plates toward the interior of the furnace.
Both the refractory plates and the compound located behind them must exhibit good thermal conductivity to convey heat from the interior of the furnace to the pipes carrying the fluid. The heated fluid is used to generate steam and/or current, or as a secondary power for heating purposes.
The known wall structure satisfies these requirements.
In addition to good thermal conductivity, a high corrosion resistance to the aggressive combustion gasses in the furnace space is required. This applies both to the plates and the refractory compound behind them. This is also intended to protect the furnace wall against corrosion.
The object of the invention is to find a way to adapt the wall structure of the mentioned type to various applications with respect to its thermal conduction. In addition, the goal is to have the wall structure be able to withstand length changes in the plates during exposure to changing temperatures without any problem.
The solution according to the invention described below is based on various considerations:
In order to make the flow of heat from the interior space of the furnace to the pipes carrying the fluid adjustable, the monolithic layer between the furnace wall and plates must have a variable width (thickness). As a result, we know that the reinforcing anchors must not be allowed to end in the monolithic compound, but must be expanded in such a way as to extend through the monolithic compound, and hence simultaneously serve to hold the preceding plates.
In this case, the anchors must be joined in corresponding recesses of the plates in such a way that no cracks form in the plates, even when the plate length changes during exposure to a variable temperature. From this standpoint, the invention also provides that a deformable compensating layer be placed in the boundary region between adjacent plates. In its most general embodiment, the wall structure is characterized by the following features:
a furnace wall, in which numerous pipes, spaced apart from each other are arranged, through which a fluid can flow,
anchors being secured to sections of the furnace wall with one end, and which are projecting essentially perpendicularly from the furnace wall,
refractory ceramic plates which exhibit recesses with the formation of a hollow space between the furnace wall and the plates spaced parallel apart from the furnace wall, and with the formation of joints between their boundary regions on their main surfaces facing the furnace wall, in which the anchors lie with their free ends embedded in a heat-resistant filling, as well deformable during exposure to heat,
heat-resistant, deformable compensating layers in the joint area between adjacent plates, and
a refractory compound filling the hollow space and covering sections of the anchors.
In this wall structure, the plates adjacent to the furnace space are xe2x80x9cfloatingxe2x80x9d mounted. They are secured and aligned relative to each other by means of the anchors. However, the anchors do not lie flush in corresponding recesses of the plates. Instead, a deformable, heat-resistant filling that compensates for length changes during exposure to temperature is provided around the corresponding sections of the anchors. The same holds true for the heat-resistant, deformable compensating layers arranged in the joint areas.
The distance between the plates and furnace wall can be set as desired over the length of the anchors. In this way, the flow of heat from the furnace space to the pipes of the furnace wall can be set. The distance between the plates and furnace wall can be alternatively or cumulatively defined via the spacers, which can be designed as an integral component of the plates.
At least two boundary regions of the plate can be coated with a deformable, heat resistant compensating layer, if necessary, except for in the area of accompanying recesses.
The plates are especially easy to secure to the anchors, which permits easy and quick assembly, along with replaceability.
Before describing the wall structure in any greater detail in various embodiments, we will first describe an accompanying refractory ceramic plate in various embodiments in greater detail.
The recesses in the plate can all be expanded to accommodate a blind hole, which is used to hold a free anchor end forming an angle, for example.
In this case, the blind hole can run essentially parallel to the main surfaces of the plate, and hence essentially parallel to the furnace wall. In this way, the plates can be mounted slightly parallel to the furnace wall.
The recesses can lie completely in the area of a main surface of the plate. However, it is also possible to design the recesses in such a way that they continue in the boundary region of the plate. This embodiment will be described in greater detail in the figure description below.
During assembly, the plates can then be placed laterally on the anchor ends forming an angle and, depending on the geometric configuration of the anchors, vertically inserted into the finally position.
As already mentioned above, a deformable compensating layer is to be situated between the corresponding boundary regions of adjacent plates. In one embodiment of the plate, this compensating layer is already permanently affixed to the plate. In a square plate with rectangular main surfaces, two adjacent boundary regions of the plate can be prefabricated in this way, for example.
In this case, the compensating layer can be made out of a fiber material, e.g., an insulating strip, which is affixed to the corresponding boundary region(s) of the plate.
As an alternative, the joint area between adjacent plates can be filled with a compressed fiber layer after the plates have been installed. To this end, a fiber mat or fiber strip, whose thickness exceeds the joint width, can initially be moistened and then (more slightly) compressed, so that it can be placed into the joint (the gap). After or while drying, the fiber layer is pressed into the joint insitu through expansion (due to the restoring forces of the fibers), and seals it off. The apparent density of the fiber layer can be increased to 2 to 3 times the original apparent density during compression (e.g., 35-70 kg/m3). Crystalline fibers are particularly suited, for example those based on aluminum oxide (e.g., 95% w/w Al2O3, 5% w/w SiO2). In like manner, the recesses in the plates can be filled with fiber material. This joint configuration can be converted independently of the above applications.
The fact that the anchors can be secured to defined points on the furnace wall, and the plates have a defined size, the plates can be precisely allocated by simply pinning or sliding the plates on the anchors, so that the plates are enhanced to form a continuous surface to the interior of the furnace.
Assembly can be further simplified and the assembly time shortened by using anchors having two arms that extend into recesses of adjacent plates. In this way, two anchoring points, one each on adjacent plates, can be provided with a single anchor. This is also explained in greater detail in the following description to the figures.
The plates can be made out of a material based on silicon carbide and/or aluminum oxide, e.g., with the addition of Cr2O3. Both exhibit good thermal conductivity, corrosion resistance and slagging resistance. The heat flow from the furnace to the pipes of the furnace wall can be set via the plate material and its thermal conduction.
A casting compound, in particular a so-called free-flowing casting compound, that can be filled into the hollow space without vibration aids is suitable as a refractory compound for filling the hollow space between the plates and furnace wall. In this case, cement-free compounds along with low-cement compounds can be used.
As do other refractory ceramic compounds, these casting compounds exhibit good thermal conductivity levels, and are highly corrosion resistant, so that they can protect the accompanying furnace wall with integrated pipes.
The heat-resistant filling in the area of the recesses (around the corresponding anchor ends) can also be made out of a ceramic compound or fiber materials. Ceramic materials for this purpose can be those based on silicon carbide, vermiculite, corundum and/or bauxite, and are known as such (e.g., CARSITECT 170V from DIDIER-WERKE AG, Wiesbaden).
Other features of the invention are specified in the features of the subclaims, and in the other application documents.